Oriental-Style Grilled Mariniated Flank Steak

2 tablespoons vegetable oil
2 tablespoons Oriental sesame oil
1/4 cup firmly packed brown sugar
1/3 cup soy sauce
1/3 cup Sherry vinegar (available at specialty foods shops)
3 scallions, chopped
a 2-inch length of fresh gingerroot, peeled and chopped
3 garlic cloves
3 tablespoons fresh lemon juice
1/2 teaspoon dried hot red pepper flakes or to taste
a 2-pound flank steak

In a blender or food processor blend together the oils, the brown sugar, the soy sauce, the vinegar, the scallions, the gingerroot, the garlic. the lemon juice, the red pepper flakes, and 1/4 cup water until the mixture is smooth. Into a shallow dish pour the marinade over the steak, turning the steak to coat it well, and let the steak marinate, covered and chilled, for at least 6 hours or overnight. Discard the marinade, grill the steak on an oiled rack set about 4 inches over glowing coals for 5 to 6 minutes on each side for medium-rare meat, and transfer it to a cutting board. Let the steak stand for 10 minutes and slice it thin across the grain.
Serves 4 to 6.